The present invention relates to an automatic transmission system for vehicles employing a gear-type transmission, in which the gear change operation of the gear-type transmission is automatically carried out in accordance with the operating condition of the vehicle at each instant.
In the prior art, there have been proposed various automatic transmission systems for vehicles comprising a gear-type transmission with an actuator for changing gears in response to electric signals, and a gear change map for determining the appropriate gear position on the basis of the amount of operation of an accelerator pedal and the vehicle speed, whereby the gear-type transmission is automatically shifted in accordance with the result of the determination based on the gear change map.
In the case where the gear position of the gear-type transmission is determined in accordance with only the amount of operation of the accelerator pedal and the vehicle speed, however, even when the driving condition of the vehicle changes, for example, due to a change in the weight of the load, hill-climbing or the like, the gear change operation of the gear-type transmission is still carried out in accordance with a gear change map determined on the basis of the standard driving condition of the vehicle. As a result, when the load condition of the vehicle changes due to a change in driving condition, it is not possible to realize appropriate gear changing operation of the gear-type transmission, making the vehicle difficult and unpleasant to drive.